PHP信号量基本用法实例详解

php;"> $key=ftok(__FILE__,'t'); /** * 获取一个信号量资源 int $key [,int $max_acquire = 1 [,int $perm = 0666 [,int $auto_release = 1 ]]] $max_acquire:最多可以多少个进程同时获取信号 $perm:权限 默认 0666 $auto_release：是否自动释放信号量 */ $sem_id=sem_get($key); #获取信号 sem_acquire($seg_id); //do something 这里是一个原子性操作 //释放信号量 sem_release($seg_id); //把次信号从系统中移除 sem_remove($sem_id); //可能出现的问题 $fp = sem_get(fileinode(__DIR__),100); sem_acquire($fp); $fp2 = sem_get(fileinode(__DIR__),1)); sem_acquire($fp2);

@mutex = sem_get($mutex_key,1); $this->resource = sem_get($resource_key,1); } /** * Destructor * * Remove the read/write semaphore */ public function __destruct() { sem_remove($this->muteX); sem_remove($this->resourcE); } /** * request acess to the resource * * @param int $mode * @return void */ private function request_access($access_type = self::rEAD_ACCESS) { if ($access_type == self::WRITE_ACCESS) { sem_acquire($this->muteX); /* update the writers counter */ $this->writers++; sem_release($this->muteX); sem_acquire($this->resourcE); } else { sem_acquire($this->muteX); if ($this->writers > 0 || $this->readers == 0) { sem_release($this->muteX); sem_acquire($this->resourcE); sem_acquire($this->muteX); } /* update the readers counter */ $this->readers++; sem_release($this->muteX); } } private function request_release($access_type = self::rEAD_ACCESS) { if ($access_type == self::WRITE_ACCESS) { sem_acquire($this->muteX); /* update the writers counter */ $this->writers--; sem_release($this->muteX); sem_release($this->resourcE); } else { sem_acquire($this->muteX); /* update the readers counter */ $this->readers--; if ($this->readers == 0) sem_release($this->resourcE); sem_release($this->muteX); } } /** * request read access to the resource * * @return void */ public function read_access() { $this->request_access(self::rEAD_ACCESS); } /** * Release read access to the resource * * @return void */ public function read_release() { $this->request_release(self::rEAD_ACCESS); } /** * request write access to the resource * * @return void */ public function write_access() { $this->request_access(self::WRITE_ACCESS); } /** * Release write access to the resource * * @return void */ public function write_release() { $this->request_release(self::WRITE_ACCESS); } }

php;"> $SHM_KEY = ftok("/home/joeldg/homeymail/shmtest.php",'R'); $shmid = sem_get($SHM_KEY,1024,0644 | IPC_CREAT); $data = shm_attach($shmid,1024); // we now have our shm segment // lets place a variable in there shm_put_var ($data,$inmem,"test"); // now lets get it BACk. we could be in a forked process and still have // access to this variable. printf("shared contents: %s\n",shm_get_var($data,$inmem)); shm_detach($data);